Question

我正在处理来自this link的以下代码。我有个问题：在上面提到的链接中，以下代码导致了一个情节。但运行此代码不会绘制任何内容。应该添加什么？

import numpy as np
import scipy.stats as st
import seaborn as sns


mus = np.array([5, 5])
sigmas = np.array([[1, .9], [.9, 1]])


def circle(x, y):
    return (x-1)**2 + (y-2)**2 - 3**2


def pgauss(x, y):
    return st.multivariate_normal.pdf([x, y], mean=mus, cov=sigmas)


def metropolis_hastings(p, iter=1000):
    x, y = 0., 0.
    samples = np.zeros((iter, 2))

    for i in range(iter):
        x_star, y_star = np.array([x, y]) + np.random.normal(size=2)
        if np.random.rand() < p(x_star, y_star) / p(x, y):
            x, y = x_star, y_star
        samples[i] = np.array([x, y])

    return samples


if __name__ == '__main__':
    samples = metropolis_hastings(circle, iter=10000)
    sns.jointplot(samples[:, 0], samples[:, 1])

    samples = metropolis_hastings(pgauss, iter=10000)
    sns.jointplot(samples[:, 0], samples[:, 1])

感谢您的帮助。

Answer 1

据@Mr报道。 T以及Seaborn plots not showing up中，您应添加plt.show()。必须从matplotlib导入plt。

所以你的代码应该是：

import numpy as np
import scipy.stats as st
import seaborn as sns
import matplotlib.pyplot as plt

mus = np.array([5, 5])
sigmas = np.array([[1, .9], [.9, 1]])


def circle(x, y):
    return (x-1)**2 + (y-2)**2 - 3**2


def pgauss(x, y):
    return st.multivariate_normal.pdf([x, y], mean=mus, cov=sigmas)


def metropolis_hastings(p, iter=1000):
    x, y = 0., 0.
    samples = np.zeros((iter, 2))

    for i in range(iter):
        x_star, y_star = np.array([x, y]) + np.random.normal(size=2)
        if np.random.rand() < p(x_star, y_star) / p(x, y):
            x, y = x_star, y_star
        samples[i] = np.array([x, y])

    return samples


if __name__ == '__main__':
    samples = metropolis_hastings(circle, iter=10000)
    sns.jointplot(samples[:, 0], samples[:, 1])

    samples = metropolis_hastings(pgauss, iter=10000)
    sns.jointplot(samples[:, 0], samples[:, 1])
    plt.show()

在没有matplotlib（seaborn）

1 个答案: